Top environmental regulators for four Republican presidents told Congress on Wednesday what many Republican lawmakers won’t: Action is needed on global warming.

In a congressional hearing organized to undermine Republican opposition to President Barack Obama’s environmental proposals, Senate Democrats asked the heads of the Environmental Protection Agency for Richard Nixon, George H.W. Bush, George W. Bush and Ronald Reagan to discuss the risks from climate change and what should be done about it. Some Republicans dispute the science of climate change and have worked to unravel Obama’s steps to address it.

Action on Capitol Hill – where even a bland, bipartisan energy efficiency bill couldn’t get passed in May – has been in a deep freeze.

“We have a scientific consensus around this issue. We also need a political consensus,” said Christine Todd Whitman, the former New Jersey Governor and first EPA administrator under President George W. Bush, who resigned her post after disagreeing with the White House’s direction on pollution rules.

Whitman was joined by William Ruckelshaus, the nation’s first EPA administrator under President Richard Nixon, William Reilly, who led the EPA under President George H.W. Bush, and Lee Thomas, who was administrator under Reagan.

The strategy by Democrats was reminiscent of other high-profile hearings on climate change that created fanfare but resulted in little action. In March, Democrats staged an all-nighter on the Senate floor to talk climate change. In 2009, former Vice President Al Gore and former House Speaker Newt Gingrich sparred before a House committee over climate change. Climate scientist James Hansen in 1988 told the Senate the planet is warming and pollution is to blame.

The EPA chiefs’ testimony apparently did little to bridge the divide. Coal miners packed the hearing to protest a new EPA plan to cut carbon dioxide pollution from power plants. Before any testimony, top Republicans on the Senate environmental panel said the rule would kill jobs for no environmental benefit.

That view contrasted sharply with the opinions of the four EPA administrators, who said the Obama administration had worked hard to make the proposal flexible and workable, using authority provided by Congress.

The former EPA administrators told lawmakers that global warming was similar to other serious environmental issues they confronted, such as industrial pollution, dangerous pesticides or water contamination. But tackling those issues enjoyed broad public support.

“Inherent in all of these problems was uncertain science and powerful economic interests resisting controls. The same is true of climate change,” said Ruckelshaus, who also led the agency under Reagan. “In all of the cases cited, the solutions to the problems did not result in the predicted economic and social calamity.”

The four EPA chiefs also said that they are not alone in the Republican party.

“There are Republicans that believe the climate is changing and humans have a role to play. They just need some political cover,” said Whitman, in an interview before the hearing.

Reilly was even more direct.

“There is a lot happening on climate,” he said, citing efforts by states and corporations to tackle the problem. “It’s just not happening in Washington.”